Surveying instrument



SURVEYING INSTRUMENT Filed Dec. 28, 1935 5 Q x I HHHHHIHIIHIDTMIHIHHHHI' i I .2264 i 5 l i 9 WW 27 15 19 Z4 5 I:- w a a 32 Q l 1 j 1 j mumnm 1 (L01 5 I12 4 INVEN 0 F/ wwi;

' ATTORNEY.

Patented May 18, 1937 UNlTED ST'iS PATENT 'OFFICE 3 Claims.

My invention relates to improvements in a surveying instrument, and it consists in the combinations, constructions, and arrangements, hereinafter described and claimed.

An object of my invention is to provide a surveying instrument used in connection with a topographic map which makes use of a sighting member for sighting any desired object within the operators vision and which also makes use of means associated with the sighting member for locating on the map the exact spot where the object will be found.

The device is especially adapted for use in loeating forest fires and can be used to point out on a map the exact position of the fire without recourse to any additional data. The device is extremely simple in construction and is durable and efficient for the purpose intended.

Other objects and advantages will appear in the following specification and the novel features of the invention will be pointed out in the appended claims.

My invention is illustrated in the accompanying drawing forming a part of this application in which Figure 1 is an end view of the device with the sliding rule omitted,

Figure 2 is a plan view showing the parts in operative position,

Figure 3 is a side elevation of the device, and

Figure 4 is a vertical section along the line 44 of Figure 3.

In carrying out my invention, I provide a base I having an arm-shaped extension 2, the extension carrying a guide strip 3 on its upper surface. A foot 4 extends from the base I and has a cylindrical and vertical rod 5 integral therewith, see Figure 4. A support 6 has a bore 1 for rotatably receiving the rod 5 and carries a hinge member 8. The hinge member 8 has an azimuth arm 9 secured thereto. It should be noted that the axis of the rod 5 lies at the intersection of two lines coinciding with the edges I and II of the arms 2 and 9 respectively.

A sliding rule I2 has a base portion I3 provided with a groove I i for receiving the strip 3. The groove I4 is. slightly wider than the width of the strip 3 and a leaf spring I is disposed in the space thus provided and is carried by the portion I3 and frictionally engages with the edge of the strip 3. In this way the rule is held in adjusted position along the arm 2. Figure 2 shows the rule I2 extending over the arm' 9 and further shows the arm 9 slidably extending under the foot 4.

A sighting bar It is pivotally secured to the top of the sleeve or support 6 at N. This bar is shown T-shaped in cross section in Figure 1 and removably carries a telescope if desired, none being shown. The pivot I! not only pivotally connects the bar I6 to the support 6 so that the bar can pivot in a vertical plane, but the bar is swung in a horizontal plane by the support 6 when the azimuth arm 9 is swung with respect to the arm 2. Figure 2 shows the bar I6 as extending in the same direction as the edge II of the azimuth arm 9.

I employ novel means for swinging the bar I6 vertically as the bar is swung horizontally by the swinging of the arm 9 toward or away from the arm 2. An arcuate cam I8 having as its center the axis of the rod 5, is carried by the base I and has a cam edge I9 of a predetermined shape. A horizontal support 20 projects from the sleeve or support 6, see Figure 3, and carries a collar 2| at its free end. A sleeve 22 is pivotally supported in the collar 2| by set screws 23 or other suitable fastening means. A rod 24 is slidably mounted in the sleeve and has its upper end pivoted at 25 to the bar I 6. The lower 1 end of the rod is rounded at 26 and rides on the cam edge I9. It is obvious that a roller, not shown, could ride on the cam edge and support the rod if desired.

A spring 30 extends from the support 6 to the bar I6 and yieldingly holds the rod 24 in contact with the cam edge I9. The outer surface of the circular cam is graduated at 3I to indicate the angular dip of the bar I6 from the horizontal in degrees or percent. carries a pointer 32 which rides over the scale 3I and by its position indicates on the scale the angular dip.

From the foregoing description of the various parts of the device, the operation thereof may be readily understood. The lower end of the rod 5 is pointed as at 21. A topographic map containing the observation point is properly oriented on a level table, and the instrument is pivoted by the point 21 at the accurately located observation point on the map. The cam edge I9 is such that the sighting bar I6 will be level when the arm 9 abuts the arm 2. The rule I 2 is graduated along the edge 28 in equal divisions and these divisions represent the vertical drop in feet from the observation point. The value of each division is determined by the relation between the actual size of the space between graduations, the scale of the map on which the device is mounted, the distance the arcuate cam is from The rod 24 3 the axis of the rod 5, and the shape of the cam edge l9.

In use, the telescope or other sighting device on the bar I6 is brought to bear on any desired point of topography visible from the observation point. First the entire instrument is swung in azimuth about the pin 2! so that the bar It is swung in a horizontal plane until the line of sight lies in the vertical plane passing through the object. The vertical angle is then obtained by swinging the arm 2 away from the arm 9. This will cause the cam edge Hi to lift the rod 24 and swing the bar l6 vertically until it points to the desired object. The sliding rule I2 is moved from its initial position at the vertex of the angle formed by the edges ii! and I! while maintaining the rest of the instrument stationary. The sliding rule is moved away from the vertex just mentioned until the first numbered mark on the scale 28 designated by the edge H corresponds with a similarly numbered contour line on the map.

For example in Figure 2, should the device be on a contour map and the scale 28 represent 900 feet of elevation, then each graduation on the scale would represent a ten foot drop from the observation point. Suppose the observation point is 2500 feet above set level. The rule I2 has been moved from the vertex until the fourteenth graduation on the scale 28 coincides with the contour line 29 representing an elevation of 2360 feet. The fourteenth mark on the scale 28 would also represent an elevation of 2360 feet. Therefore the spot located on the map by the intersection of the scale edge 28 and the edge II will be the exact spot being sighted by the sighting bar.

It is obvious that if points to be located on the map are above the observation point, then the cam edge l9 would be inclined in the opposite direction and would incline the sighting bar above the horizon. It will be seen that I provide positive means for transposing a small vertical angle, made by the inclined sighting bar with the horizontal, to an exaggerated horizontal angle formed between the azimuth arm and the second arm 2 pivoted to the first.

While I have shown only the preferred form of my invention, it is to be understood that various changes may be made without departing from the spirit and scope of the appended claims.

I claim:

1. The combination with a horizontally disposed topographic map properly oriented, of an azimuth arm rotatable about a vertical axis passing through a point on the map representing the observation point, a second arm pivoted to the azimuth arm and being swingable about the same axis and in a horizontal plane overlying the map, a sighting member swingable with the aximuth arm about the same axis and pointing in the same direction as the arm at all times, connections between the sighting member and the second arm for causing the sighting member to swing through a vertical angle in direct ratio to the angle made between the arms, and a scale indicating prependicular distance, said scale extending at right angles to and being slidable along the second arm, said scale also being slidable along the azimuth arm, whereby the object sighted by the sighting member is located on the map by the point of intersection of the scale with the azimuth arm when the first elevation number on a contour line is similar to and coincides with a scale number at the point of intersection.

2. In combination, an azimuth arm pivotal about a fixed point, a second arm pivoted thereto in a horizontal plane and about the same point, a sighting member swingable with the azimuth arm about the same point and pointing in the same direction as the arm at all times, connections between the sighting member and the second arm for causing the sighting member to swing through a vertical angle in direct ratio to the angle made between the arms, and a scale indicating perpendicular distance, said scale extending at right angles to and being slidable along the second arm, and also being slidable along the azimuth arm.

3. A surveying instrument comprising an azimuth arm, a second arm pivoted thereto and swingable in a horizontal plane, a sighting member swingable in a vertical plane passing through the azimuth arm, an arcuate cam concentric with the pivot and being rigidly connected to the second arm, connections between the cam and the sighting member for causing the cam to swing the sighting member through an angle with respect to the horizontal in direct ratio to the swinging of the second arm with respect to the azimuth arm, and a scale slidable along the second arm and extending at right angles thereto, said scale indicating perpendicular distance and being slidable along the azimuth arm, the perpendicular distance being indicated by the number on the scale overlying the azimuth arm.

NELSON DENMAN SALMON. 

